Data transmission apparatus, data division apparatus and data division method

ABSTRACT

A data transmission apparatus includes: a transmission data division unit which divides transmission data into blocks; a transmission unit which transmits the blocks divided by the transmission data division unit to the transmission destination apparatus; a calculation unit which calculates a size of residual data generated by dividing the transmission data into the blocks each having the predetermined data size; and a residual data judgment unit which judges whether the size of the residual data calculated by the calculation unit is smaller or not smaller than a minimum data size which the receiving apparatus can receive. In the case that it is judged that the size of the residual data is smaller than the minimum data size, the transmission data division unit generates a block, which includes the residual data and whose data size is equal to or larger than the minimum data size, by dividing the transmission data so as to make the block, which includes the residual data, include a part of the transmission data other than the residual data.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This application is a National Stage Entry of International ApplicationNo. PCT/JP2013/004191, filed Jul. 5, 2013, which claims priority fromJapanese Patent Application No. 2012-164736, filed Jul. 5, 2012. Theentire contents of the above-referenced applications are expresslyincorporated herein by reference.

TECHNICAL FIELD

The present invention is related to a data transmission apparatus, adata division apparatus and a data division method, and particularly arerelated to a data transmission apparatus, a data division apparatus anda data division method which divide transmission data into blocks.

BACKGROUND ART

In the case of packet transmission, a packet transmission apparatusdivides packet data, which are received from its preceding communicationapparatus, into a plurality of blocks each having a fixed block size(predetermined block size), and assigns the blocks to a plurality oftransmission lines. Accordingly, the packet transmission apparatus canincrease transmission capacity by use of the plural transmission lines.

In the case that a size of the packet data, which are received from thecommunication apparatus, is not an integral multiple of the fixed datablock size, if dividing the packet data into the blocks each having thefixed block size, n (n is any integer) blocks each having the fixedblock size, and one block including residual data, whose size is smallerthan the fixed block size, are generated.

In the case of a method according to a related art, by carrying out apadding process in which dummy data are added to the residual data, thepacket transmission apparatus makes the size of the residual dataadjusted to the fixed block size. Then, the packet transmissionapparatus transfers data for which the padding process is carried out.The method has a problem that data transmission efficiency is lowered,since the transferred data includes a block which has an area unused fordata transmission.

In order to solve the problem, PTL 1 discloses an art to set a size ofpacket data, which are sent by a communication apparatus, to be equal toor smaller than MTU (Maximum Transfer Unit) defined between thecommunication apparatus and a transmission destination apparatus, and tobe an integral multiple of a block size which is applied to a low ranktransmission line. By using the method, it is avoided to generate theresidual data in the division process carried out by the packettransmission apparatus which receives the packet data from thecommunication apparatus. Therefore, it is possible to avoid generationof the block which includes the unused area.

CITATION LIST Patent Literature

-   PTL 1: Japanese Patent Application Laid-Open Publication No.    2002-084312

Technical Problem

According to the art disclosed in PTL 1, it is assumed that thecommunication apparatus adjusts the size of the data packet, andaccording to the art, a situation that the communication apparatus sendspacket data, which has an optional size, to the packet transmissionapparatus is not taken into consideration. Accordingly, in the case thatthe communication apparatus sends the packet data, which has theoptional size, to the packet transmission apparatus, the residual datais generated in the division process which is carried out by the packettransmission apparatus. Therefore, it is not possible to restraingeneration of the block including the unused area, and consequently theproblem that packet transmission efficiency is lowered still remains.

The present invention is conceived to solve the problem. An object ofthe present invention is to provide a data transmission apparatus, adata division apparatus and a data division method which can make datatransmission efficient.

Solution To Problem

A first aspect of the present invention includes a data transmissionapparatus which divides transmission data into blocks each of which hasa predetermined data size, and transmits the blocks to a transmissiondestination apparatus. The data transmission apparatus includes: atransmission data division unit which divides the transmission data intothe blocks; a transmission unit which transmits the blocks divided bythe transmission data division unit to the transmission destinationapparatus: a calculation unit which calculates a size of residual datagenerated by dividing the transmission data into the blocks each havingthe predetermined data size; and a residual data judgment unit whichjudges whether the size of the residual data calculated by thecalculation unit is smaller or not smaller than a minimum data sizewhich the transmission destination apparatus can receive. In the casethat the residual data judgment unit judges that the size of theresidual data is smaller than the minimum data size, the transmissiondata division unit generates a block, which includes the residual dataand whose data size is equal to or larger than the minimum data size, bydividing the transmission data so as to make the block, which includesthe residual data, include a part of the transmission data other thanthe residual data.

A second aspect of the present invention includes a data divisionapparatus which divides transmission data into blocks each of which hasa predetermined data size. The data division apparatus includes: atransmission data division unit which divides the transmission data intothe blocks; a calculation unit which calculates a size of residual datagenerated by dividing the transmission data into the blocks each havingthe predetermined data size; and a residual data judgment unit whichjudges whether the size of residual data calculated by the calculationunit is smaller or not smaller than a minimum data size which atransmission destination apparatus can receive. In the case that theresidual data judgment unit judges that the size of the residual data issmaller than the minimum data size, the transmission data division unitgenerates a block, which includes the residual data and whose data sizeis equal to or larger than the minimum data size, by dividing thetransmission data so as to make the block, which includes the residualdata, include a part of the transmission data other than the residualdata.

A third aspect of the present invention includes a data division methodused by a data division apparatus which divides transmission data intoblocks each of which has a predetermined data size. The data divisionmethod includes the following steps (a), (b) and (c):

(a) calculating a size of residual data generated by dividing thetransmission data into the blocks each of which has the predetermineddata size;

(b) judging whether the calculated size of the residual data is smalleror not smaller than a minimum data size which a transmission destinationapparatus can receive; and

(c) generating a block, which includes the residual data and whose datasize is equal to or larger than the minimum data size, by dividing thetransmission data so as to make the block, which includes the residualdata, include a part of the transmission data other than the residualdata, in the case that it is judged that the size of the residual datais smaller than the minimum data size.

Advantageous Effects Of Invention

According to each aspect of the present invention, it is possible toprovide the data transmission apparatus, the data division apparatus andthe data division method which can realize efficient data transmission.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram showing a configuration example of a datatransmission apparatus according to an exemplary embodiment 1.

FIG. 2 is a flowchart showing an example of a process which is carriedout by the data transmission apparatus according to the exemplaryembodiment 1.

FIG. 3 is a block diagram showing an example of a wireless communicationsystem according to an exemplary embodiment 2.

FIG. 4 is a block diagram showing a configuration example of a packetdata division circuit according to the exemplary embodiment 2.

FIG. 5 is a block diagram showing a detailed configuration example of awireless packet transmission apparatus according to the exemplaryembodiment 2.

FIG. 6 is a flowchart showing an example of a division process methodaccording to the exemplary embodiment 2.

FIG. 7A is a first image diagram showing an example of a packet datadivision method according to the exemplary embodiment 2.

FIG. 7B is a second image diagram showing an example of the packet datadivision method according to the exemplary embodiment 2.

FIG. 7C is a third image diagram showing an example of the packet datadivision method according to the exemplary embodiment 2.

FIG. 8A is a first image diagram showing details of the packet datadivision method according to the exemplary embodiment 2.

FIG. 8B is a second image diagram showing details of the packet datadivision method according to the exemplary embodiment 2.

FIG. 9A is a first image diagram showing a packet data division methodaccording to a related art.

FIG. 9B is a second image diagram showing the packet data divisionmethod according to the related art.

FIG. 10 is a block diagram showing an example of a wirelesscommunication system according to an exemplary embodiment 3.

FIG. 11 is a block diagram showing a detailed configuration example of awireless packet transmission apparatus according to the exemplaryembodiment 3.

FIG. 12 is a block diagram showing an example of a wirelesscommunication system according to an exemplary embodiment 4.

DESCRIPTION OF EMBODIMENTS

Exemplary Embodiment 1

Hereinafter, an exemplary embodiment according to the present inventionwill be explained with reference to drawings.

FIG. 1 is a block diagram showing a configuration example of a datatransmission apparatus according to an exemplary embodiment 1. A datatransmission apparatus 10 is a data transmission apparatus which dividestransmission data, which a transmission data generation apparatus 1generates, into blocks (block data) each having a predetermined datasize, and transmits the blocks to a receiving apparatus 2 (transmissiondestination apparatus). The data transmission apparatus 10 and thereceiving apparatus 2 are connected each other via a wired or wirelesstransmission line. The data transmission apparatus 10 includes atransmission data division unit 11, a transmission unit 12, acalculation unit 13 and a residual data judgment unit 14.

The transmission data division unit 11 divides the transmission data,which are generated by the transmission data generation apparatus 1,into the blocks. Details of a division process, which is carried out bythe transmission data division unit 11, will be described later.

The transmission unit 12 transmits transmission data divided by thetransmission data division unit 11 into blocks, to the receivingapparatus 2.

The calculation unit 13 calculates a size of residual data generated bydividing the transmission data, which are generated by the transmissiondata generation apparatus 1, into the blocks each having thepredetermined data size. Here, the predetermined data size is a datasize which is set by a user. For example, the data size is a valuedepending on a state of the transmission line between the datatransmission apparatus 10 and the receiving apparatus 2. As one exampleof the predetermined data size, a value of the data size is set to sucha degree that transmission delay is not caused on the transmission line.

The residual data judgment unit 14 judges whether the size of theresidual data, which is calculated by the calculation unit 133, issmaller or not smaller than a minimum data size which the receivingapparatus 2 can receive. Each unit of the data transmission apparatus 10mentioned above is realized by hardware such as IC (Integrated Circuit)or the like, software such as application software or the like or thehardware and the software.

The transmission data generation apparatus 1 is an apparatus whichgenerates the transmission data and sends the transmission data to thedata transmission apparatus 10.

The receiving apparatus 2 receives the transmission data divided intoblocks, from the data transmission apparatus 10. Here, the receivingapparatus 2 does not receive data, whose size is smaller than theminimum data size, as effective receiving data. Accordingly, in order totransmit the transmission data effectively, it is necessary for the datatransmission apparatus 10 to transmit a block whose size is equal to orlarger than the minimum data size. The minimum data size is a valuewhich is set by a user and is smaller than the predetermined data sizementioned above.

Details of the division process which the transmission data divisionunit 11 carries out will be explained in the following with reference toFIG. 2. FIG. 2 is a flowchart showing an example of a process which iscarried out by each unit of the data transmission apparatus 10.

Firstly, the calculation unit 13 calculates the size of the residualdata generated by dividing the transmission data, which are outputted bythe transmission data generation apparatus 1, into the blocks eachhaving the predetermined data size (Step S1).

Next, the residual data judgment unit 14 judges whether the size of theresidual data calculated by the calculation unit 13 is smaller or notsmaller than the minimum data size which the receiving apparatus 2 canreceive (Step S2).

In the case that the residual data judgment unit 14 judges that the sizeof the residual data is smaller than the minimum data size (Yes in StepS2), the transmission data division unit 11 divides the transmissiondata so as to make a block, which includes the residual data, include apart of the transmission data other than the residual data. As a result,the residual data judgment 14 generates a block which includes theresidual data and whose data size is equal to or larger than the minimumdata size (Step S3).

At this point of time, the transmission data division unit 11 carriesout the data division so that a block other than the block, whichincludes the residual data, may have a size equal to or larger than theminimum data size.

The transmission unit 12 transmits the transmission data divided by thetransmission data division unit 11 into blocks, to the receivingapparatus 2 (Step S4). Since each of the blocks generated by thetransmission data division unit 11 has a size equal to or larger thanthe minimum data size, the receiving apparatus 2 can receive all of theblocks with no error.

In Step S2, in the case that the residual data judgment unit 14 judgesthat the size of the residual data is larger than the minimum data size(No in Step S2), the transmission data division unit 11 divides thetransmission data as follows. The transmission data division unit 11divides the transmission data into a block which includes the residualdata and no other data (in FIG. 2, described as ‘include only residualdata’), and one or more blocks each having a size which is equal to orsmaller than the predetermined data size and is equal to or larger thanthe minimum data size (Step S5).

The transmission unit 12 transmits the transmission data divided by thetransmission data division unit 11 into blocks, to the receivingapparatus 2 (Step S4). The block, which is generated in Step S5 andincludes the residual data, has a size equal to or larger than theminimum data size. Accordingly, since each of the blocks generated bythe transmission data division unit 11 has a size equal to or largerthan the minimum data size, the receiving apparatus 2 can receive all ofthe blocks with no error.

By carrying out the above-mentioned process, even in the case that thesize of the residual data is smaller than the minimum data size, thedata transmission apparatus 10 can transmit the transmission data bydividing the transmission data into blocks each of whose sizes is equalto or larger than the minimum data size. In other words, even if thesize of the transmission data has any value, the data transmissionapparatus 10 can transmit the transmission data by diving thetransmission data into the blocks each of which has a size equal to orlarger than the minimum data size. Therefore, the transmission datadivision unit 11 can avoid carrying out a process of transmitting ablock to which excessive data (unused area) other than the transmissiondata are added. Accordingly, it is possible to realize efficient datatransmission.

Here, the data transmission apparatus 10 may add identificationinformation, such as a header or the like, to the post-division block.In this case, the receiving apparatus 2 restores the transmission datafrom the received blocks on the basis of the identification information.

The transmission data generation apparatus 1 and the data transmissionapparatus 10 may be constituted so as to be united into one apparatus.

Furthermore, the data transmission apparatus 10 may have a configurationthat the transmission unit 12 is arranged externally. In this case, thedata transmission apparatus 10 works as a data division apparatus whichdivides the transmission data into blocks.

The invention which has been described in the above can be regarded asan invention on a data division method for dividing the transmissiondata. The data division method includes the following steps (a), (b) and(c):

-   -   (a) calculating a size of residual data generated by dividing        the transmission data into blocks each of which has the        predetermined data size;    -   (b) judging whether the calculated size of the residual data is        smaller or not smaller than a minimum data size which a        transmission destination apparatus can receive; and    -   (c) generating a block, which includes the residual data and        whose data size is equal to or larger than the minimum data        size, by dividing the transmission data so as to make the block,        which includes the residual data, include a part of the        transmission data other than the residual data, in the case that        it is judged that the size of the residual data is smaller than        the minimum data size.

A chip which carries out the method may be mounted on the transmissiondata apparatus 10.

Exemplary Embodiment 2

Hereinafter, an exemplary embodiment 2 of the present invention will beexplained with reference to drawings. Here, a part which has alreadybeen explained in the exemplary embodiment 1 is properly omitted.

FIG. 3 shows one example of a wireless communication system whichincludes L2SW (Layer 2 switch) apparatuses 3 and 4, and wireless packettransmission apparatuses 20 and 30. In FIG. 3, the L2SW apparatus 3 andthe wireless packet transmission apparatus 20 are connected each othervia a LAN circuit s10, and the L2SW apparatus 4 and the wireless packettransmission apparatus 30 are connected each other via a LAN circuits20.

The L2SW apparatus 3 is a communication apparatus followed by thewireless packet transmission apparatus 20, and outputs packet data,which are corresponding to the transmission data, to the wireless packettransmission apparatus 20 via the LAN circuit s10. The L2SW apparatus 4is a communication apparatus preceded by the wireless packettransmission apparatus 30, and obtains packet data, which arecorresponding to the transmission data, from the wireless packettransmission apparatus 30 via the LAN circuit s20. The L2SW apparatus 3is an apparatus opposite to the wireless packet transmission apparatus,and the L2SW apparatus 4 is an apparatus opposite to the wireless packettransmission apparatus 30.

Here, transmission capacity of the LAN circuit s10 is larger thantransmission capacity of a wireless circuit r10, and is larger thantransmission capacity of a wireless circuit r20. However, a total of thetransmission capacity of the wireless circuit r10 and the transmissioncapacity of the wireless circuit r20 is larger than the transmissioncapacity of the LAN circuit s10. Moreover, transmission capacity of theLAN circuit s20 is larger than the transmission capacity of the wirelesscircuit r10, and is larger than the transmission capacity of thewireless circuit r20. However, a total of the transmission capacity ofthe wireless circuit r10 and the transmission capacity of the wirelesscircuit r20 is larger than the transmission capacity of the LAN circuits10. The wireless communication system shown in FIG. 3 transfers thepacket data by use of both of the wireless circuit r10 and the wirelesscircuit r20 (by binding the wireless circuit r10 and the wirelesscircuit r20). As mentioned above, the wireless packet transmissionapparatus 20 intends to increase the transmission capacity by use of aplurality of circuits.

The wireless packet transmission apparatus 20 and the wireless packettransmission apparatus 30 are connected each other via the wirelesscircuit r10 and the wireless circuit r20. The wireless packettransmission apparatus 20 transfers the packet data to the wirelesspacket transmission apparatus 30 via the wireless circuits r10 and r20by use of radio waves. That is, the wireless packet transmissionapparatus 20 and the wireless packet transmission apparatus 30 areopposite each other via the wireless circuits.

The wireless packet transmission apparatus 20 is a transmissionapparatus which is corresponding to the data transmission apparatus 10shown in FIG. 1. It is illustrated that the wireless packet transmissionapparatus 20 includes a transmission packet data buffer circuit(transmission buffer circuit) 21, a packet data division circuit(division circuit) 22, and a wireless sending circuits (sendingcircuits) 23 and 24. It is illustrated that the wireless packettransmission apparatus 30 is a receiving apparatus which iscorresponding to the receiving apparatus 2 shown in FIG. 1. FIG. 3 showsthat the wireless packet transmission apparatus 30 includes wirelessreceiving circuits (received circuits) 31 and 32, received block databuffer circuits (receiving buffer circuits) 33 and 34, and a packet datarestoration circuit 35. Here, the wireless packet transmission apparatus30 is set so as not to receive a block which has a size smaller than aminimum block size (minimum data size). Hereinafter, each unit of thewireless packet transmission apparatuses 20 and 30 will be explained.

The transmission packet data buffer circuit 21 carries out a bufferingprocess to a transmission packet signal p10 which the L2SW apparatus 3outputs, and outputs the buffered transmission packet signal p10 to thepacket data division circuit 22 as a packet data signal (transmissionpacket data signal p11). The transmission packet data buffer circuit 21detects a size of the packet data which the L2SW apparatus 3 outputs inthe buffering process.

The packet data division circuit 22 divides the packet data, which thetransmission packet data buffer circuit 21 outputs, into a plurality ofblocks. Then, the packet data division circuit 22 outputs a part of thegenerated plural blocks to the wireless sending circuit 23 as atransmission division block signal p12, and outputs the left blocks tothe wireless sending circuit 24 as a transmission division block signalp13.

FIG. 4 is a block diagram showing a configuration example of the packetdata division circuit 22. The packet data division circuit 22 includes apacket data division unit 221, a calculation unit 222 and a residualdata judgment unit 223. The packet data division unit 221, thecalculation unit 222 and the residual data judgment unit 223 arecorresponding to the transmission data division unit 11, the calculationunit 13 and the residual data judgment unit 14 shown in FIG. 1,respectively. Details of the packet data division process, which thepacket data division circuit 22 carries out, will be described later.

Here, the packet data division circuit 22 includes a memory (not shownin the drawings) which stores a fixed block size and the minimum blocksize which are set by a user, and the size of the packet data, inputtedto the transmission packet data buffer circuit 21. The fixed block sizeis corresponding to the predetermined data size which is described inthe exemplary embodiment 1. The packet data division circuit 22 readsdata, which is stored in the memory, according to a process carried outby each unit, and uses the data.

The packet data division circuit 22 assigns information on a head, anend and a sequence number of the block to each of the plural blocks,into which the packet data division unit 221 divides the packet data, asa header. By the above, it is possible for the packet data divisioncircuit 22 to make the packet data restoration circuit 35, which isincluded in the receiving side wireless packet transmission apparatus30, restore the packet data.

The wireless sending circuit 23 multiplexes the block, which the packetdata division circuit 22 outputs, into a wireless frame, and carries outa wireless sending process such as a modulation process, DA (Digital toAnalog) conversion, frequency conversion and the like. Then, thewireless sending circuit 23 sends data, which are generated by thewireless sending process, to the wireless packet transmission apparatus30 via the wireless circuit r10 as a transmission wireless signal p14.Similarly, the wireless sending circuit 24 carries out a process such asthe wireless transmission process or the like to the block which thepacket data division circuit 22 outputs. Then, the wireless sendingcircuit 24 sends data, which are generated by the wireless transmissionprocess, to the wireless packet transmission apparatus 30 via thewireless circuit r20 as a transmission wireless signal p15. The wirelesssending circuits 23 and 24 are corresponding to the transmission unit 12shown in FIG. 1.

The wireless receiving circuit 31 carries out a wireless receivingprocess such as frequency conversion, AD (Analog to Digital) conversion,a demodulation process and the like to a received wireless signal p25(identical to sending wireless signal p14), which the wireless receivingcircuit 31 receives via the wireless circuit r10, and consequentlyextracts the block from the wireless frame. The wireless receivingcircuit 31 outputs the extracted block to the received block data buffercircuit 33 as a received wireless block signal p23. Similarly, thewireless receiving circuit 32 carries out the wireless receiving processto a received wireless signal p26 (identical to transmission wirelesssignal p15), which the wireless receiving circuit 32 receives via thewireless circuit r20, and consequently extracts the block from thewireless frame. Then, the wireless receiving circuit 32 outputs theextracted block to the received block data buffer circuit 34 as areceived wireless block signal p24.

The receiving block data buffer circuit 33 carries out a bufferingprocess to the block which is received from the wireless receivingcircuit 31, and afterward outputs the buffered block to the packet datarestoration circuit 35 as a received division block signal p21.Similarly, the received block data buffer circuit 34 carries out abuffering process to the block which is received from the wirelessreceiving circuit 32, and afterward outputs the buffered block to thepacket data restoration circuit 35 as a received division block signalp22.

The packet data restoration circuit 35 restores the packet data, whichthe received block data buffer circuit 33 and the received block databuffer circuit 34 output, to the original packet data which the wirelesspacket transmission apparatus 20 obtains from the L2SW apparatus 3.

Specifically, the packet data restoration circuit 35 refers to theheader which the packet data division circuit 22 of the wireless packettransmission apparatus 20 assigns to the packet data. The packet datarestoration circuit 35 judges a head position and an end position of thepost-division block out of the data on the basis of the referred header.As mentioned above, the packet data restoration circuit 35 detects thepost-division block.

Furthermore, by referring to the sequence number which is embedded inthe header, the packet data restoration circuit 35 judges whether lossor disappearance of block is caused due to a fault of the wirelesscircuit or the like or not. In the case that loss of sequence number(state that discontinuity of sequence number is caused) is not caused,the packet data restoration circuit 35 restores the blocks to theoriginal packet data by aligning the blocks in an order of thecontinuous sequence number.

In the case that loss of sequence number is caused, the packet datarestoration circuit 35 discards a block which is being received, andpacket data which are in a restoration process. The packet datarestoration circuit 35 resumes the packet data restoration process froma top block which is received next.

The packet data restoration circuit 35 outputs the packet data, whichare re-generated by the restoration process, to the L2SW apparatus 4 asa received packet signal p20.

Here, for making explanation simplified, FIG. 3 shows only a packet datasending side circuit (transmission packet data buffer circuit 21, packetdata division circuit 22 and wireless sending circuits 23 and 24) in thewireless packet transmission apparatus 20. Similarly, FIG. 3 shows onlya packet data receiving side circuit (wireless receiving circuits 31 and32, receiving block data buffer circuits 33 and 34 and packet datarestoration circuit 35) in the wireless packet transmission apparatus30. Actually, the wireless packet transmission apparatus 20 and thewireless packet transmission apparatus 30 have the same configuration.That is, the wireless packet transmission apparatus 20 includes thepacket data received side circuit not shown, and the wireless packettransmission apparatus 30 includes the packet data sending side circuitnot shown.

FIG. 5 is a block diagram showing a detailed configuration example ofthe wireless packet transmission apparatus 20. The wireless packettransmission apparatus 20 includes wireless receiving circuits 25 and26, received block data buffer circuits 27 and 28 and a packet datarestoration circuit 29 in addition to the transmission packet databuffer circuit 21, the packet data division circuit 22 and the wirelesssending circuits 23 and 24 which are shown in FIG. 3. The wirelessreceiving circuits 25 and 26, the received block data buffer circuits 27and 28 and the packet data restoration circuit 29 have the same circuitconfigurations and carry out the same processes as the wirelessreceiving circuits 31 and 32, the received block data buffer circuits 33and 34 and the packet data restoration circuit 35, respectively. Here,the wireless receiving circuits 25 and 26 receive data from the wirelesspacket transmission apparatus 30 via wireless circuits r30 and r40,respectively. In the case of the wireless packet transmission apparatus30, the above-mentioned packet data sending side circuit divides thepacket data into the blocks, and sends the block to the wireless packettransmission apparatus 20 via the wireless circuits r30 and r40. Eachunit of the wireless transmission apparatuses 20 and 30 mentioned aboveis realized by hardware such as IC (Integrated Circuit) or the like,software such as application software or the like or the hardware andthe software.

FIG. 6 is a flowchart showing an example of a packet data divisionprocess method which the packet data division circuit 22 carries out.Hereinafter, the packet data division process which the packet datadivision circuit 22 carries out will be explained with reference to FIG.6. Here, the packet data division circuit 22 carries out the packet datadivision process on the basis of the fixed block size and the minimumblock size which are set in advance. In the following process, each unitof the packet data division circuit 22 reads data on the fixed blocksize, the minimum block size and the size of the packet data, which arestored in a memory, according to necessity.

Firstly, the calculation unit 222 of the packet data division circuit 22judges whether a size X of the packet data, which are inputted from thetransmission packet data buffer circuit 21, is an integral multiple (nmultiple) of a fixed block size M or not (Step S11). In other words, thecalculation unit 222 calculates a size x of the residual data which aregenerated by dividing the packet data into the blocks each having thefixed block size M, and judges whether x is 0 or not.

In the case that the calculation unit 222 judges that the size X of thepacket data is n times as large as the fixed block size M, that is, inthe case that the calculation unit 222 judges that the size x of theresidual data is 0 (Yes in Step S11), the packet data division unit 222divides the packet data into n blocks (Step S12). Each of the n blockshas the same fixed block size M.

The packet data division circuit 22 assigns information on a head, anend, a sequence number or the like of the block to each block as aheader. Then, by distributing and outputting the blocks to the wirelesssending circuits 23 and 24, the packet data division circuit 22distributes and sends the packet data to the plural wireless circuits(wireless circuits r10 and r20).

In the case that it is judged that the size X of the packet data is notan integral multiple of the fixed block size M, that is, in the casethat it is judged that the size x of the residual data is not 0 (No inStep S11), the residual data judgment unit 223 judges whether the size xof the residual data is equal to or larger than the minimum block size mor not (Step S14)

In the case that the residual data judgment unit 223 judges that thesize x of the residual data is equal to or larger than the minimum blocksize m (Yes in Step S14), the packet data division unit 221 divides thepacket data into one or more blocks each of which has the fixed blocksize, and one block which includes only the residual data (Step S15).Here, since the size x of the residual data is equal to or larger thanthe minimum block size m, the wireless packet transmission apparatus 20can receive the residual data. Accordingly, the wireless packettransmission apparatus 30 can transmit all of the blocks into which thedata packet is divided. The packet data division circuit 22 assigns aheader to each block, and distributes and sends the blocks to the pluralwireless circuits (Step S13).

In the case that the residual data judgment unit 223 judges that thesize x of the residual data is smaller than the minimum block size m (Noin Step S14), the packet data division unit 221 divides the packet dataas follows. The packet data division unit 221 divides the packet datainto one or more blocks each of which has the fixed block size M, ablock which includes the residual data and a block whose size is equalto or smaller than the fixed block size M and is equal to or larger thanthe minimum block size m. Here, the block, which includes the residualdata, includes a part of the packet data other than the residual data(Step S16). As mentioned above, the packet data division unit 221divides the packet data so that the block, which includes the residualdata, may have a size equal to or larger than the minimum block size m.

Here, the part of the packet data, which are included in the blockincluding the residual data and which are different from the residualdata, are data which just follow or just precede the residual data in asequence of the packet data. In other words, the part of the data packetother than the residual data are data which exist just before or justafter the residual data in the sequence of the packet data, that is,there is no data between the residual data and the part of the packetdata.

The packet data division circuit 22 assigns a header to each block whichis generated in the process mentioned above, and distributes and sendsthe blocks to the plural wireless circuits (Step S13).

Each of FIGS. 7A to 7C is an image diagram showing an example of thepacket data division method for dividing the packet data on the basis ofa procedure which is described in the flowchart shown in FIG. 6. FIG. 7Ashows the packet data division method applied to a case that the size Xof the packet data, which are received from the L2SW apparatus 3, is1280 bytes. Similarly, FIG. 7B shows the packet data division methodapplied to a case that the size X of the packet data, which are receivedfrom the L2SW apparatus 3, is 1279 bytes, and FIG. 7C shows the packetdata division method applied to a case that the size X of the packetdata, which are received from the L2SW apparatus 3, is 1281 bytes. Here,in every case, the fixed block size M is 256 bytes, and the minimumblock size m is 64 bytes.

FIG. 7A indicates that the packet data of 1280 bytes are divided into 5blocks of 256 bytes. In Step S11 shown in FIG. 6, the calculation unit222 judges whether the size X of the packet data is an integral multipleof the fixed block size M or not. Here, since the size X of the packetdata is 1280 bytes, and the fixed block size is 256 bytes, the size ofthe packet data is just 5 times as large as the fixed block size.

Accordingly, in Step S11 shown in FIG. 6, the packet data divisioncircuit 22 judges that the size X of the packet data is an integralmultiple of the fixed block size M (Yes in Step S11).

The packet data division unit 221 divides the packet data into 5 blocks(Step S12). Each of these 5 blocks has a block size of 256 bytes. Then,the packet data division circuit 22 assigns information on a head, anend and a sequence number of the block to each block as a header (headeris denoted as ‘H’ in FIGS. 7A to FIG. 7C). The packet data divisioncircuit 22 distributes and sends the 5 blocks, to each of which theheader is assigned, to the wireless circuits (Step S13).

FIG. 7B indicates that the packet data of 1279 bytes are divided into 4blocks of 256 bytes and one block of 255 bytes. The calculation unit 222judges whether the size X of the packet data is an integral multiple ofthe fixed block size M or not. In this case, since the size of the datapacket is 1279 bytes, and the fixed block size is 256 bytes, the size ofthe packet data is not an integral multiple of the fixed block size.Accordingly, in Step S11 shown in FIG. 6, the calculation unit 222judges that the size X of the packet data is not an integral multiple ofthe fixed block size M (No in Step S11). At this point of time, thecalculation unit 222 calculates the size x of the residual data, andfinds that the size x is 255 bytes.

The residual data judgment unit 223 judges whether the size x of theresidual data, which are left when dividing the packet data by the fixedblock size M, is equal to or larger than the minimum block size m or not(Step S14). In FIG. 7B, since the size x of the residual data is 255bytes, and the minimum block size m is 64 bytes, the size x of theresidual data is larger than the minimum block size m. Accordingly, theresidual data judgment unit 223 judges that the size x of the residualdata is equal to or larger than the minimum block size m (Yes in StepS14), and divides the packet data into 4 blocks and one block whichincludes only the residual data (Step S15). Each of these 4 blocks hasthe same fixed block size M. The packet data division circuit 22 assignsa header to each block, and distributes and sends the blocks, to each ofwhich the header is assigned, to the plural wireless circuits (StepS13).

FIG. 7C indicates that the packet data of 1281 bytes are divided into 4blocks of 256 bytes, one block of 128 bytes and one block of 129 bytes.In the flow shown in FIG. 6, the packet data division circuit 22 judgeswhether the size X of the packet data which are inputted from thetransmission packet data buffer circuit 21 is an integral multiple ofthe fixed block size M or not (Step S11). In this case, since the size Xof the data packet is 1281 bytes, and the fixed block size M is 256bytes, the size X of the packet data is not an integral multiple of thefixed block size M. Accordingly, in Step S11 shown in FIG. 6, thecalculation unit 222 judges that the size X of the packet data is not anintegral multiple of the fixed block size M (No in Step S11). At thispoint of time, the calculation unit 222 calculates the size x of theresidual data, and finds that the size x is 1 byte.

The residual data judgment unit 223 judges whether the size x of theresidual data, which are left when dividing the packet data by the fixedblock size M, is equal to or larger than the minimum block size m or not(Step S14). In FIG. 7C, since the size x of the residual data is 1 byte,and the minimum block size m is 64 bytes, the size x of the residualdata is smaller than the minimum block size m. Accordingly, the residualdata judgment unit 223 judges that the size x of the residual data issmaller than the minimum block size m (No in Step S14)

The packet data division unit 221 divides the packet data into 4 blockseach of which has the fixed block size M, a block having a size x1 whichis equal to or smaller than the fixed block size M and which is equal toor larger than the minimum block size m, and a block which includes theresidual data and which has a size x2 (Step S16). Here, the size x1 is128 bytes, and the size x2 is 129 bytes. This is because data, whichinclude the residual data of 1 byte and a part of the packet data of 256bytes (fixed block size M), are divided into 2 blocks of almost the samesize. The packet data division circuit 22 assigns a header to each blockwhich is generated in the above-mentioned process, and distributes andsends the generated blocks to the plural wireless circuits (Step S13).

FIG. 8A and FIG. 8B show details of the division processes shown in FIG.7B and FIG. 7C, respectively. In FIG. 8A and FIG. 8B, a left end of thepacket data indicates a head of the packet data, and a right endindicates an end of the packet data.

In FIG. 8A, the packet data division unit 221 divides 1024 bytes fromthe head of the packet data into 4 blocks each of which has the fixedblock size M. Then, the packet data division unit 221 generates oneblock including only the residual data of 255 bytes in the tail of thepacket data. The packet data division circuit 22 assigns a header toeach of the generated blocks.

In FIG. 8B, the packet data division unit 221 divides 1024 bytes fromthe head of the packet data into 4 blocks each of which has the fixedblock size M. Then, the packet data division unit 221 divides theresidual data of 1 byte in the tail, and data of second last end side256 bytes into a block which has the size x1 of 128 bytes, and a blockwhich has the size x2 of 129 bytes. Here, the block which has the sizeof 129 bytes includes the residual data of 1 byte, and the data of 128bytes which are corresponding to the part of the packet data other thanthe residual data. The data of 128 bytes, which are corresponding to thepart of the packet data other than the residual data, are data whichexist on the second last end side of the packet data while the residualdata exist on the last end side (that is, the data of 128 bytes existjust before the residual data.). Accordingly, there is no data betweenthe residual data and the data of 128 bytes.

As mentioned above, the packet data division circuit 22 divides thepacket data according to the method which is based on the size of thepacket data, that is, which is different dependently on the size of thepacket data.

Here, the packet data division circuit 22 may carry out the flow processshown in FIG. 6 together with dividing the packet data. For example, inthe case that the size of the packet data is 1281 bytes, the packet datadivision unit 221 divides block data from the head side of the packetdata into blocks each of which has the fixed block size of 256 bytes,and assigns a header to each the block, and distributes the blocks tothe wireless circuits. Simultaneously, the calculation unit 222calculates the size x of the residual data on the basis that the size ofthe packet data is 1281 bytes, and finds that the size x of the residualdata is 1 byte. The residual data judgment unit 223 judges that the sizex of the residual data is smaller than the minimum block size m, anddivides the residual data of 1 byte in the tail and the data of thesecond end side 256 bytes out of the packet data into the block whichhas the size of 128 bytes and the block which has the size of 129 bytes.Then, the packet data division circuit 22 assigns a header to eachdivision block, and distributes the blocks to the wireless circuits.

Or, the packet data division circuit 22 may divide all of the packetdata into the blocks, and afterward distribute and send the blocks tothe wireless circuits 23 and 24. Here, by carrying out the flow processshown in FIG. 6 together with dividing the packet data, it is possibleto send the packet data to the wireless packet transmission apparatus 30in a short time.

Each of FIG. 9A and FIG. 9B is an image diagram showing a packet datadivision method according to a related art. FIG. 9A shows the packetdata division method which is applied to a case that the packet data,which are received from the L2SW apparatus 3, have a size of 1280 bytes,and FIG. 9B shows the packet data division method which is applied to acase that the packet data, which are received from the L2SW apparatus 3,has a size of 1281 bytes. Here, in FIG. 9A and FIG. 9B, a header(denoted as ‘H’) is assigned to a block.

FIG. 9A indicates that packet data of 1280 bytes are divided into 5blocks of 256 bytes. In this case, since the size of the packet data canbe divided by the fixed block size M, a padding process is not carriedout. Accordingly, data which are in a used area do not exist in theblock.

However, in the case that the size of the packet data cannot be dividedby the fixed block size, the unused area is caused in the block. FIG. 9Bindicates that the packet data of 1281 bytes are divided into 6 blocksof 256 bytes. The packet data are divided into the blocks each of whichhas the fixed block size of 256 bytes, and the residual data which hasthe size x of 1 byte. According to the method of the related art, oneblock, which has the fixed block size of 256 bytes, is generated byadding an unused area U of 255 bytes (by carrying out the paddingprocess) to the residual data of 1 byte. Then, the packet transmissionapparatus transmits the generated 6 blocks. In this case, since theunused area is caused the block, packet data transmission efficiencybecomes degraded.

In contrast, the padding process is not carried out in the generationprocess shown in FIG. 7A to FIG. 7C. Therefore, it is possible to avoidtransmission of useless data which are corresponding to the unused area,and to realize enhancement of data transmission efficiency.

Furthermore, as shown in FIG. 7C, on the basis of the data of 256 bytes(corresponding to one block which has the fixed block size M) and theresidual data, the packet data division circuit 22 generates the blockwhich includes the residual data, and the block whose data size is equalto or smaller than the fixed block size M and is equal to or larger thanthe minimum block size m. The packet data division circuit 22 generates4 blocks each of which has the fixed block size M in addition to thegenerated blocks mentioned above. As mentioned above, by generating theblock, which includes the residual data, on the basis of only theresidual data and the data corresponding to one block which has thefixed block size M, the packet data division circuit 22 can generate oneblock, whose size is equal to or larger than the minimum block size mand which includes the residual data, in small number of processes.Moreover, according to the method, it is possible to carry out theprocess of generating the block, which includes the residual data,together with dividing the packet data from the head side of the packetdata into the blocks and distributing the blocks to the wirelesscircuits, as mentioned above. Specifically, in FIG. 7C, by dividing thepacket data, the transmission data division unit 221 generates theblock, which has the size of 256 bytes, before generating the block of129 bytes which includes the residual data, and the block which has thedata size of 128 bytes. Then, the sending circuits 23 and 24 transmitthe blocks, which the transmission data division unit 221 generates, inturn. Therefore, an effect that it is possible to start transmissionearly in comparison with a case of starting transmission after divisioninto the blocks is completed.

Here, the packet data division unit 221 divides a total of the residualdata of one byte, and the part of the packet data of 256 bytes (fixedblock size M) into two blocks of almost the equal data size. Here,‘almost equal’ includes a case that a size of one block is differentfrom a size of another block by one byte to several bytes. In otherwords, ‘almost equal’ includes a case that there is a difference betweensizes of two blocks, which are generated by division, to such an extentthat transmission times of the two blocks from the wireless packettransmission apparatus 20 to the wireless packet transmission apparatus30 are regarded to be equal each other. By virtue of the above, it ispossible to make the transmission times of the two blocks, which aregenerated by division, from the wireless packet transmission apparatus20 to the wireless packet transmission apparatus 30 almost equal.Therefore, it is possible to make the packet data restoration circuit 35of the receiving side wireless packet transmission apparatus 30 carryout the restoration process early and accurately in comparison with acase that there is the difference between the transmission times of thetwo blocks from the wireless packet transmission apparatus 20 to thewireless packet transmission apparatus 30.

In FIG. 7C, the part of the packet data, which are included in the blockincluding the residual data and which are different from the residualdata, are data which just follow or just precede the residual data.Here, even if the part of the packet data are not data which just followor just precede the residual data, it is possible to realize enhancementof data transmission efficiency. However, in the case that the part ofthe packet data are data which just follow or just precede the residualdata, a time required for the packet data restoration process, which iscarried out by the packet data restoration circuit 35 of the wirelesspacket transmission apparatus 30, becomes short, and consequently it ispossible to carry out the restoration process efficiently.

Here, while it has been explained in FIG. 7C that the fixed block size Mis 256 bytes, and the minimum block size m is 64 bytes, other values maybe applicable. However, in order to generate two blocks, each of whosesizes is equal to or larger than the minimum block size m, on the basisof the residual data and the data whose size is the fixed block size, itis necessary that the fixed block size is 2 or more times as large asthe minimum block size.

In the case that the size of the residual data is equal to or largerthan the minimum block size as shown in FIG. 7B, the packet datadivision circuit 22 assigns a header to the residual data as it is totransmit the residual data including the header. Therefore, it ispossible to reduce a process time which the packet data division circuit22 consumes.

In the case that there is no residual data (that is, size of residualdata is 0), the packet data division unit 221 divides the packet datainto the blocks each of which has the fixed block size to transmit theblocks. Therefore, the packet data division circuit 22 can transmit thepacket data efficiently.

Exemplary Embodiment 3

Hereinafter, an exemplary embodiment 3 of the present invention will beexplained with reference to drawings. The exemplary embodiment 3 showsanother application example of the data transmission apparatus accordingto the present invention. Here, parts which have already been explainedin the exemplary embodiments 1 and 2 are properly omitted.

FIG. 10 shows a wireless communication system which includes the L2SWapparatuses 3 and 4 and wireless packet transmission apparatuses 40, 50,60 and 70. In FIG. 10, the L2SW apparatus 3 and the wireless packettransmission apparatus 40 are connected each other via the LAN circuits10, and the L2SW apparatus 4 and the wireless packet transmissionapparatus 60 are connected each other via the LAN circuit s20. Thewireless packet transmission apparatus 40 and the wireless packettransmission apparatus 60 are connected each other via the wirelesscircuit r10 and the wireless circuit r30. The wireless packettransmission apparatus 50 and the wireless packet transmission apparatus60 are connected each other via the wireless circuit r20 and thewireless circuit r40. The wireless circuits r10 to r40 are the same asthe wireless circuits r10 to r40 shown in FIG. 5, respectively.

The wireless packet transmission apparatus 40 includes a sending andreceiving control circuit 41, a wireless sending circuit 42 and awireless receiving circuit 43. The wireless packet transmissionapparatus 50 includes a transmission and received data buffer circuit51, a wireless sending circuit 52 and a wireless receiving circuit 53.The wireless packet transmission apparatus 60 includes a wirelessreceiving circuit 61, a wireless sending circuit 62 and a sending andreceiving control circuit 63. The wireless packet transmission apparatus70 includes a wireless receiving circuit 71, a wireless sending circuit72 and a transmission and received data buffer circuit 73.

Details of configurations of the wireless packet transmission apparatus40 and the wireless packet transmission apparatus 50 will be explainedin the following with reference to FIG. 11. FIG. 11 is a block diagramshowing an example of configurations of the wireless packet transmissionapparatus 40 and the wireless packet transmission apparatus 50.

The sending and receiving control circuit 41 of the wireless packettransmission apparatus 40 includes a transmission packet data buffercircuit 44, a packet data division circuit 45, a received block databuffer circuit 46 and a packet data restoration circuit 47. Thetransmission packet data buffer circuit 44, the packet data divisioncircuit 45, the received block data buffer circuit 46 and the packetdata restoration circuit 47 have the same circuit configurations andcarry out the same processes as the transmission packet data buffercircuit 21, the packet data division circuit 22, the received block databuffer circuit 27 and the packet data restoration circuit 29 in FIG. 5,respectively. The wireless sending circuit 42 and the wireless receivingcircuit 43 have the same circuit configurations and carry out the sameprocesses as the wireless sending circuit 23 and the wireless receivingcircuit 25 in FIG. 5, respectively.

The wireless packet transmission apparatus 40 has a configuration inwhich the wireless sending circuit 24, the wireless receiving circuit 26and the received block data buffer circuit 28 are deleted from thewireless packet transmission apparatus 20 shown in FIG. 5. Atransmission division block signal p30, which is outputted from thepacket data division circuit 45, is inputted into the wireless packettransmission apparatus 50, and a receiving division block signal p40,which is inputted into the packet data restoration circuit 47, isoutputted from the wireless packet transmission apparatus 50.

The transmission and received data buffer circuit 51 of the wirelesspacket transmission apparatus 50 includes a transmission packet databuffer circuit 54 and a received block data buffer circuit 55. Thewireless sending circuit 52, the wireless receiving circuit 53, thetransmission packet data buffer circuit 54 and the received block databuffer circuit 55, which are installed in the wireless packettransmission apparatus 50, have the same circuit configurations andcarry out the same processes as the wireless sending circuit 24, thewireless receiving circuit 26, the transmission packet data buffercircuit 21 and the received block data buffer circuit 28 in FIG. 5,respectively.

Here, an operation of the wireless packet transmission apparatus 50 willbe explained. The transmission packet data buffer circuit 54 carries outa buffering process to the transmission division block signal p30 whichis inputted from the wireless packet transmission apparatus 40, andoutputs the buffered transmission division block signal p30 to thewireless sending circuit 52 as a transmission division block signal p31.

Here, the transmission division block signal p30, which is inputted fromthe wireless packet transmission apparatus 40, is the same as thetransmission division block signal p13 which is generated by the packetdata division circuit 22 of the wireless packet transmission apparatus20 shown in FIG. 5.

The wireless sending circuit 52 carries out a wireless sending process,such as a process of multiplexing to a wireless frame, a modulationprocess, DA conversion, frequency conversion and the like, to thetransmission division block signal p31 which is inputted from thetransmission packet data buffer circuit 54. Afterward, the transmissiondivision block signal p31 is sent to the wireless circuit r20 as atransmission wireless signal p32.

The wireless receiving circuit 53 carries out a wireless receivingprocess, such as frequency conversion, AD conversion, a demodulationprocess and the like, to a received wireless signal p42 which isinputted from the wireless circuit r40. Afterward, the received wirelesssignal p42 is outputted to the received block data buffer circuit 55 asa received wireless block signal p41.

The received block data buffer circuit 55 carries out a bufferingprocess to the received wireless block signal p41 which is inputted fromthe wireless receiving circuit 53, and outputs the buffered receivedwireless block signal p41 to the packet data restoration circuit 47 asthe received division block signal p40.

Here, the received division block signal p40, which is outputted to thewireless packet transmission apparatus 40, is the same as the receiveddivision block signal p22 which is received by the packet datarestoration circuit 29 of the wireless packet transmission apparatus 20shown in FIG. 5.

Here, the wireless receiving circuit 61, the wireless sending circuit 62and the sending and receiving control circuit 63 of the wireless packettransmission apparatus 60 have the same circuit configurations and carryout the same processes as the wireless receiving circuit 43, thewireless sending circuit 42 and the sending and receiving controlcircuit 41 , respectively. The wireless receiving circuit 71, thewireless sending circuit 72 and the transmission and received databuffer circuit 73 have the same circuit configurations and carry out thesame processes as the wireless receiving circuit 53, the wirelesssending circuit 52 and the transmission and received data buffer circuit51, respectively. Each unit of the wireless packet transmissionapparatuses 50 and 60 is realized by hardware such as IC (IntegratedCircuit) or the like, software such as application software or the likeor the hardware and the software.

By the above, the wireless communication system, which carries out thewireless communication by use of plural wireless packet transmissionapparatuses, has been explained. Since also the wireless communicationsystem can carry out the process which is the same as the process in theexemplary embodiment 2, it is possible to realize enhancement of datatransmission efficiency.

Exemplary Embodiment 4

Hereinafter, an exemplary embodiment 4 of the present invention will beexplained with reference to a drawing. The exemplary embodiment 4 showsanother application example of the data transmission apparatus accordingto the present invention. Here, parts which have already been explainedin the exemplary embodiments 1 to 3 are properly omitted.

FIG. 12 shows a communication system which includes the L2SW apparatuses3 and 4, and packet transmission apparatuses 80 and 90. In FIG. 12, theL2SW apparatus 3 and the packet transmission apparatus 80 are connectedeach other via the LAN circuit s10, and the L2SW apparatus 4 and thepacket transmission apparatus 90 are connected each other via the LANcircuit s20.

The packet transmission apparatus 80 includes a transmission packet databuffer circuit 81 and a packet data division circuit 82, and the packettransmission apparatus 90 includes a received block data buffer circuits91 and 92, and a packet data restoration circuit 93.

The packet transmission apparatus 80 is a packet transmission apparatusin which the wireless sending circuits 23 and 24 are deleted from thewireless packet transmission apparatus 20 shown in FIG. 3. The packettransmission apparatus 90 is a packet transmission apparatus which has aconfiguration obtained by deleting the wireless receiving circuits 31and 32 from the wireless packet transmission apparatus 30 shown in FIG.3.

The transmission packet data buffer circuit 81 and the packet datadivision circuit 82 have the same circuit configurations and carry outthe same processes as the transmission packet data buffer circuit 21 andthe packet data division circuit 22 in FIG. 3, respectively. The packetdata division circuit 82 outputs a transmission division block signalp50 and a transmission division block signal p51 which are generated bydividing transmission data into blocks. The transmission division blocksignal p50 is outputted to the packet transmission apparatus 90 via aLAN circuit s30, and the transmission division block signal p51 isoutputted to the packet transmission apparatus 90 via a LAN circuit s40.

The received block data buffer circuits 91 and 92 have the same circuitconfigurations as the received block data buffer circuits 33 and 34 inFIG. 3, respectively. The received block data buffer circuit 91 carriesout a buffering process to a received transmission division block signalp60 (the same signal as transmission division block signal p50), andafterward outputs the buffered transmission division block signal p60 tothe packet data restoration circuit 93 as the received division blocksignal p21. The received block data buffer circuit 92 carries out thesame process.

The packet data restoration circuit 93 has the same circuitconfiguration and carries out the same process as the packet datarestoration circuit 35 in FIG. 33, respectively.

Here, for making explanation simplified, FIG. 12 shows only a packetdata sending side circuit (transmission packet data buffer circuit 81and packet data division circuit 82) in the case of the packettransmission apparatus 80, and only a packet data receiving side circuit(received block data buffer circuits 91 and 92, and packet datarestoration circuit 93) in the case of the packet transmission apparatus90. Actually, the packet transmission apparatus 80 and the packettransmission apparatus 90 have the same configuration. That is, thepacket transmission apparatus 80 includes furthermore the packet datareceiving side circuit not shown in the figure, and the packettransmission apparatus 90 includes the packet data sending side circuitnot shown in the figure. The receiving side circuit and the sending sidecircuit have the same configurations as ones shown in FIG. 12. Each unitof the packet transmission apparatuses 80 and 90 is realized by hardwaresuch as IC (Integrated Circuit) or the like, software such asapplication software or the like or the hardware and the software.

By the above, the communication system, which carries out the wirelesscommunication by use of not the wireless circuit but the plural LANcircuits, has been explained. Since also the wireless communicationsystem can carry out the same process as the process in the exemplaryembodiments 2 and 3, it is possible to realize enhancement of datatransmission efficiency.

At present, while there are many communication services and an amount ofnetwork traffic becomes increasing, an art to make line capacityincreasing is required. The present invention is conceived to realizeenhancement of data transmission efficiency on the basis of such thebackground art. The present invention is applicable to a technical fieldon data transmission. The present invention is applicable to, forexample, packet data transmission which includes wireless packet datatransmission.

Here, the present invention is not limited to the above-mentionedexemplary embodiment, and it is possible to make changes properly withinthe scope of intention.

For example, in FIG. 7C of the exemplary embodiment 2, the packet datadivision unit 221 does not have to divide a total of the residual dataof 1 byte and the data of 256 bytes into 2 blocks which have the samesize. The packet data division unit 221 can carry out another divisionmethod as far as a block, whose size is equal to or smaller than thefixed block size M and is equal to or larger than the minimum block sizem, is generated according to the method. For example, the packet datadivision unit 221 may divide a total of the residual data of 1 byte andthe data of 256 bytes into a block of 64 bytes which includes theresidual data of 1 byte, and a block of 193 byte (first data size). Alsoby carrying out the above-mentioned process, since many blocks each ofwhich has the fixed block size M are generated, a time required for thepacket data division 22's carrying out the process is shortened incomparison with a case of generating many blocks each of which has asize different from the fixed block size M. That is, it is possible tocarry out the division process efficiently.

However, by the packet data division unit 221's dividing data, whichinclude the residual data of 1 byte and the data of 256 bytes, into 2blocks which have the same data size, it is possible to maketransmission times, which are required for transmitting the 2 blocks tothe wireless packet transmission apparatus 30, the same each other.Accordingly, from a point of view of transmission efficiency, it isdesirable that the packet data division circuit 221 divides data, whichincludes the residual data, into 2 blocks which have the same data size.

In FIG. 7C, the block of 128 bytes and the block of 129 bytes, which aregenerated by division, does not have to be transmitted at the same time,that is, may be transmitted at times different each other. Furthermore,when carrying out the packet data division process, the transmissiondata division unit 221 may generate the block of 128 bytes and the blockof 129 bytes at first. Or, the transmission data division unit 221 maygenerate the block of 128 bytes firstly and generate the block of 129bytes finally. However, it is desirable that an order of data in thepacket data, which are transmitted from the wireless packet transmissionapparatus 20 to the wireless packet transmission apparatus 30, isidentical with an order of data in the original packet data. The reasonis to make the packet data restoration process carried out faster andmore accurately.

In FIG. 7C, the packet data division unit 221 may divide the packet datainto one or more blocks each having a second data size which isdifferent from the fixed block size M and is equal to or larger than theminimum block size m, and one or more blocks each having a third datasize which is equal to or smaller than the fixed block size M and isequal to or larger than the minimum block size m. For example, in thecase that the size X of the packet data is 1816 bytes, the packet datadivision unit 221 may divide the packet data so as to generate 7 blocksof 250 bytes different from the fixed block size M (256 bytes), and oneblock of 66 bytes equal to or smaller than the fixed block size M andequal to or larger than the minimum block size m. Here, it isunnecessary that the blocks, each of which has the second data size,have exactly equal data size. The blocks, each of which has the seconddata size, may have above-mentioned ‘almost equal’ data size. Forexample, instead of generating 7 blocks of 250 bytes, the packet datadivision unit 221 may generate one block of 248 bytes, one block of 252bytes and 5 blocks of 250 bytes. The above is similar to the third datasize.

In the case that the size X of the packet data is 1816 bytes, the packetdata division unit 221 can divide the packet data into 7 blocks each ofwhich has the fixed block size M, and one block of 24 bytes. Here, sincethe block of 24 bytes has a size smaller than the minimum block size m,the wireless packet transmission apparatus cannot transmit the block of24 bytes as it is. Accordingly, the above-mentioned division process canbe regarded as a process in which the packet data division unit 221assigns 6 bytes of each of 7 blocks, each of which has the fixed blocksize M, to the block of 24 bytes to generate blocks each of whose sizesis equal to or larger than the minimum block size m.

Also by carrying out the above-mentioned process, it is possible toreduce types of size of the blocks generated by dividing the packetdata. Therefore, in comparison with a case of dividing the packet dataso as to make the size of block randomized, it is possible for thepacket data division circuit 22 to carry out the division process moreefficiently. Furthermore, each transmission time of blocks, each ofwhich has the same size, from the wireless packet transmission apparatus20 to the wireless packet transmission apparatus 30 is regarded to bethe same. That is, by transmitting blocks, each of which has the samesize, from the wireless packet transmission apparatus 20 in an order,the blocks reaches the receiving side wireless packet transmissionapparatus 30 in the order of transmission from the wireless packettransmission apparatus 20. Therefore, it is possible for the packet datarestoration circuit 35 of the wireless packet transmission apparatus 30to carry out the packet data restoration process with accuracy.

In the case of the exemplary embodiment 2, the wireless packettransmission apparatus 20 transmits the blocks by use of two wirelesscircuits r10 and r20. Accordingly, it is desirable from a point of viewof data transmission efficiency that at least one out of number of theplural blocks having the second data size and number of the pluralblocks having the third data size is even, since it is possible to sendone block via the wireless circuit r10 and the other one block via thewireless circuit r20 at the same time. In the case that n (integer)wireless circuits are used, it is desirable due to the same reason thatat least one out of number of the plural blocks having the second datasize and number of the plural blocks having the third data size is a nmultiple.

In the case that the size of the packet data can be divided by aspecific data size which is equal to or smaller than the fixed blocksize M and is equal to or larger than the minimum block size m, thepacket data division unit 221 may divide the packet data into the blockseach of which has the specific data size. For example, in the case thatthe size X of the packet data is 1400 bytes, the packet data divisionunit 221 may divide the packet data so as to generate 7 blocks of 200bytes. That is, the second data size and the third data size may be thesame each other.

However, by setting the second data size to be the fixed block size M,and the third data size to be a value which is smaller than the fixedblock size M and is equal to or larger than the minimum block size m, itis possible for the packet data division circuit 22 to carry out thedivision process with efficiency. The reason is that it is unnecessaryfor the packet data division circuit 22 to carry out the divisionprocess on the basis of the specific data size.

Furthermore, by showing an example, the division process mentioned abovewill be explained. In the case that the size X of the packet data is 300bytes, the packet data division unit 221 divides the packet data togenerate data whose data size is 256 bytes (corresponding to one blockhaving the fixed block size M), and the residual data of 44 bytes. Theresidual data has a data size which is smaller than a residual data m.Accordingly, in this case, the packet data division unit 221 may dividethe packet data into a block which has a data size of 200 bytes (seconddata size), and a block which has a data size of 100 bytes (third datasize). Also by carrying out the above-mentioned process, it is possibleto transmit the packet data since the packet data division unit 221 candivide the packet data into the blocks each of which has a value equalto or larger than the minimum block size m. Furthermore, the packet datadivision unit 221 may divide the packet data into a block which has adata size of 150 bytes (second data size), and a block which has a datasize of 150 bytes (third data size).

In FIG. 7C, on the basis of data of 512 bytes (corresponding to 2 blockseach of which has the fixed block size M) and the residual data, thepacket data division unit 221 may generate 1 block which includes theresidual data, and 2 blocks each of whose sizes is equal to or smallerthan the fixed block size M and is equal to or smaller than the minimumblock size m (generate a total of 3 blocks). Also by carrying out theabove-mentioned process, the packet data division unit 221 can generateblocks each of which has a data size equal to or larger than the minimumblock size m. Similarly, by carrying out (n+1) division to datacorresponding to n blocks (n is an integer) each having the fixed blocksize M, and the residual data, the packet data division unit 221 maygenerate (n+1) blocks each of whose data sizes is equal to or smallerthan the fixed block size M and is equal to or larger than the minimumblock size m. As far as blocks each of whose data sizes is equal to orsmaller than the fixed block size M and is equal to or larger than theminimum block size m are generated, the packet data division unit 221may divide data into (n+2) or more blocks. However, by generating ablock, which includes the residual data, on the basis of only theresidual data and data which is corresponding to one block having thefixed block size M, the packet data division unit 221 can generate ablock, whose size is equal to or larger than the minimum block size mand which includes the residual data, in small number of processes.

Here, a size of data, which is used when dividing the residual data andthe data into blocks, is changed according to a ratio of the minimumblock size m to the fixed block size M. For example, a case that a valueof the minimum block size m is two thirds of the fixed block size M willbe considered. In this case, it is necessary to generate a total of 3blocks, that is, 1 block which includes the residual data, and 2 blocks,each of whose data sizes is equal to or smaller than the fixed blocksize M and is equal to or larger than the minimum block size m, on thebasis of data of 512 bytes (corresponding to 2 blocks each of which hasthe fixed block size M) and the residual data. The reason is that, inthe case of using only the residual data and data of 256 bytes(corresponding to one block which has the fixed block size M), it isimpossible for the packet data division unit 221 to generate blocks eachof whose data sizes is equal to or larger than the minimum block size m.

It is possible to make the data transmission apparatus (or, datadivision apparatus) carry out the process flows shown in the exemplaryembodiments 1 to 4 as one of control methods. For example, the datatransmission apparatus (or, data division apparatus) may be instructedto carry out the flow as a control program

Here, the control program, which is executed by the data transmissionapparatus (or, data division apparatus), is stored by use of varioustypes of non-transitory computer readable medium, and can be provided toa computer. The non-transitory computer readable medium includes varioustypes of tangible storage medium. An example of the non-transitorycomputer readable medium includes a magnetic record medium (for example,flexible disk, magnetic tape, hard disk drive), a magnetic opticalrecord medium (for example, magnetic optical disk), CD-ROM, CD-R,CD-R/W, a semiconductor memory (for example, mask ROM, PROM(Programmable ROM), EPROM (Erasable PROM), a flash ROM, RAM (RandomAccess memory). Moreover, a display control program may be provided to acomputer by use of the various types of non-transitory computer readablemedium. An example of the transitory computer readable medium includesan electric signal, an optical signal and an electromagnetic wave. Thetransitory computer readable medium can provide a computer with thecontrol program via a wired communication line, such as a wire, anoptical fiber or the like, or a wireless communication line.

Hereinafter, various embodiments will be added.

(Supplementary Note 1)

A data transmission apparatus which divides transmission data intoblocks each of which has a predetermined data size, and transmits theblocks to a transmission destination apparatus, comprising:

a transmission data division unit which divides the transmission datainto the blocks;

a transmission unit which transmits the blocks divided by thetransmission data division unit to the transmission destinationapparatus;

a calculation unit which calculates a size of residual data generated bydividing the transmission data into the blocks each having thepredetermined data size; and

a residual data judgment unit which judges whether the size of theresidual data calculated by the calculation unit is smaller or notsmaller than a minimum data size which the transmission destinationapparatus can receive, wherein

in the case that the residual data judgment unit judges that the size ofthe residual data is smaller than the minimum data size, thetransmission data division unit generates a block, which includes theresidual data and whose data size is equal to or larger than the minimumdata size, by dividing the transmission data so as to make the block,which includes the residual data, include a part of the transmissiondata other than the residual data.

(Supplementary Note 2)

The data transmission apparatus according to supplementary note 1,wherein

the transmission data division unit divides the transmission data intoone or more blocks each of which has the predetermined data size, ablock which includes the residual data, and a block having a first datasize which is equal to or smaller than the predetermined data size andis equal to or larger than the minimum data size.

(Supplementary Note 3)

The data transmission apparatus according to supplementary note 2,wherein

the block including the residual data has a data size almost equal tothe first data size.

(Supplementary Note 4)

The data transmission apparatus according to supplementary note 1,wherein

the transmission data division unit divides the transmission data intoone or more blocks each of which has a second data size equal to orsmaller than the predetermined data size and equal to or larger than theminimum data size, and one or more blocks each of which has a third datasize equal to or smaller than the predetermined data size and equal toor larger than the minimum data size.

(Supplementary note 5)

The data transmission apparatus according to supplementary note 4,wherein

the second data size is the predetermined data size and is differentfrom the third data size.

(Supplementary Note 6)

The data transmission apparatus according to any one of supplementarynotes 1 to 5, wherein

the part of the transmission data, which are included in the blockincluding the residual data and which are different from the residualdata, are data which just follow or just precede the residual data inthe transmission data.

(Supplementary Note 7)

The data transmission apparatus according to any one of supplementarynotes 1 to 6, wherein

in the case that the residual data judgment unit judges that the size ofthe residual data is equal to or larger than the minimum data size, thetransmission data are divided into a block which includes the residualdata, and a block which has the predetermined data size.

(Supplementary Note 8)

The data transmission apparatus according to any one of supplementarynotes 1 to 7, wherein

in the case that the size of the residual data, which is calculated bythe calculation unit, is 0, the transmission data division unit dividesthe transmission data into a plurality of blocks each of which has thepredetermined data size.

(Supplementary Note 9)

A data division apparatus which divides transmission data into blockseach of which has a predetermined data size, comprising:

a transmission data division unit which divides the transmission datainto the blocks;

a calculation unit which calculates a size of residual data generated bydividing the transmission data into the blocks each having thepredetermined data size; and

a residual data judgment unit which judges whether the size of theresidual data calculated by the calculation unit is smaller or notsmaller than a minimum data size which a transmission destinationapparatus can receive, wherein

in the case that the residual data judgment unit judges that the size ofthe residual data is smaller than the minimum data size, thetransmission data division unit generates a block, which includes theresidual data and whose data size is equal to or larger than the minimumdata size, by dividing the transmission data so as to make the block,which includes the residual data, include a part of the transmissiondata other than the residual data.

(Supplementary Note 10)

A data division method used by a data division apparatus which dividestransmission data into blocks each of which has a predetermined datasize, comprising:

calculating a size of residual data generated by dividing thetransmission data into the blocks each having the predetermined datasize;

judging whether the calculated size of the residual data is smaller ornot smaller than a minimum data size which a transmission destinationapparatus can receive; and

generating a block, which includes the residual data and whose data sizeis equal to or larger than the minimum data size, by dividing thetransmission data so as to make the block, which includes the residualdata, include a part of the transmission data other than the residualdata, in the case that it is judged that the size of the residual datais smaller than the minimum data size.

(Supplementary Note 11)

The data transmission apparatus according to supplementary note 2 or 3,wherein

the transmission data division unit generates one or more blocks each ofwhich has the predetermined data size before generating the blockincluding the residual data, and the block which has the third datasize, and wherein

the transmission unit transmits the blocks, which the transmission datadivision unit generates, in turn.

While the invention has been particularly shown and described withreference to exemplary embodiments thereof, the invention is not limitedto these embodiments. It will be understood by those of ordinary skillin the art that various changes in form and details may be made thereinwithout departing from the spirit and scope of the present invention asdefined by the claims.

This application is based upon and claims the benefit of priority fromJapanese Patent Application Publication No. 2012-164736, filed on Jul.25, 2012, the disclosure of which is incorporated herein in its entiretyby reference.

INDUSTRIAL APPLICABILITY

The present invention is applicable to a technical field of datatransmission. For example, the present invention is applicable to packetdata transmission including wireless packet data transmission.

REFERENCE SIGNS LIST

-   1 transmission data generation apparatus-   2 receiving apparatus-   3 and 4 L2SW apparatus-   10 data transmission apparatus-   11 transmission data division unit-   12 transmission unit-   13 calculation unit-   14 residual data judgment unit-   20 wireless packet transmission apparatus-   21 transmission packet data buffer circuit-   22 packet data division circuit-   221 packet data division unit-   222 calculation unit-   223 residual data judgment unit-   23 and 24 wireless sending circuit-   25 and 26 wireless receiving circuit-   27 and 28 received block data buffer circuit-   29 packet data restoration circuit-   30 wireless packet transmission apparatus-   31 and 32 wireless receiving circuit-   33 and 34 received block data buffer circuit-   35 packet data restoration circuit-   40 wireless packet transmission apparatus-   41 sending and receiving control circuit-   42 wireless sending circuit-   43 wireless receiving circuit-   44 transmission block data buffer circuit-   45 packet data division circuit-   46 received block data buffer circuit-   47 packet data restoration circuit-   50 wireless packet transmission apparatus-   51 transmission and received data buffer circuit-   52 wireless sending circuit-   53 wireless receiving circuit-   54 transmission packet data buffer circuit-   55 received block data buffer circuit-   60 wireless packet transmission apparatus-   61 wireless receiving circuit-   62 wireless sending circuit-   63 sending and receiving control circuit-   70 wireless packet transmission apparatus-   71 wireless receiving circuit-   72 wireless sending circuit-   73 transmission and received data buffer circuit-   80 packet transmission apparatus-   81 transmission packet data buffer circuit-   82 packet data division circuit-   90 packet transmission apparatus-   91 and 92 received block data buffer circuit-   93 packet data restoration circuit

The invention claimed is:
 1. A data transmission apparatus which dividestransmission data into blocks each of which has a predetermined datasize, and transmits the blocks to a transmission destination apparatus,comprising: a transmission data division unit which divides thetransmission data into the blocks; a transmission unit which transmitsthe blocks divided by the transmission data division unit to thetransmission destination apparatus; a calculation unit which calculatesa size of residual data generated by dividing the transmission data intothe blocks each having the predetermined data size; and a residual datajudgment unit which judges whether the size of the residual datacalculated by the calculation unit is smaller or not smaller than aminimum data size which the transmission destination apparatus canreceive, wherein in the case that the residual data judgment unit judgesthat the size of the residual data is smaller than the minimum datasize, the transmission data division unit generates a block, whichincludes the residual data and whose data size is equal to or largerthan the minimum data size, by dividing the transmission data so as tomake the block, which includes the residual data, include a part of thetransmission data other than the residual data.
 2. The data transmissionapparatus according to claim 1, wherein the transmission data divisionunit divides the transmission data into one or more blocks each of whichhas the predetermined data size, a block which includes the residualdata, and a block having a first data size which is equal to or smallerthan the predetermined data size and is equal to or larger than theminimum data size.
 3. The data transmission apparatus according to claim2, wherein the block including the residual data has a data size almostequal to the first data size.
 4. The data transmission apparatusaccording to claim 1, wherein the transmission data division unitdivides the transmission data into one or more blocks each of which hasa second data size equal to or smaller than the predetermined data sizeand equal to or larger than the minimum data size, and one or moreblocks each of which has a third data size equal to or smaller than thepredetermined data size and equal to or larger than the minimum datasize.
 5. The data transmission apparatus according to claim 4, whereinthe second data size is the predetermined data size and is differentfrom the third data size.
 6. The data transmission apparatus accordingto claim 4, wherein the transmission data division unit generates one ormore blocks each of which has the predetermined data size beforegenerating the block including the residual data, and the block whichhas the third data size, and wherein the transmission unit transmits theblocks, which the transmission data division unit generates, in turn. 7.The data transmission apparatus according to claim 1, wherein the partof the transmission data, which are included in the block including theresidual data and which are different from the residual data, are datawhich just follow or just precede the residual data in the transmissiondata.
 8. The data transmission apparatus according to claim 1, whereinin the case that the residual data judgment unit judges that the size ofthe residual data is equal to or larger than the minimum data size, thetransmission data are divided into a block which includes the residualdata, and a block which has the predetermined data size.
 9. The datatransmission apparatus according to claim 1, wherein in the case thatthe size of the residual data, which is calculated by the calculationunit, is 0, the transmission data division unit divides the transmissiondata into a plurality of blocks each of which has the predetermined datasize.
 10. A data division apparatus which divides transmission data intoblocks, comprising: a transmission data division unit which divides thetransmission data into the blocks; a calculation unit which calculates asize of residual data generated by dividing the transmission data intothe blocks each having the predetermined data size; and a residual datajudgment unit which judges whether the size of the residual datacalculated by the calculation unit is smaller or not smaller than aminimum data size which a transmission destination apparatus canreceive, wherein in the case that the residual data judgment unit judgesthat the size of the residual data is smaller than the minimum datasize, the transmission data division unit generates a block, whichincludes the residual data and whose data size is equal to or largerthan the minimum data size, by dividing the transmission data so as tomake the block, which includes the residual data, include a part of thetransmission data other than the residual data.
 11. A data divisionmethod used by a data division apparatus which divides transmission datainto blocks each of which has a predetermined data size, comprising:calculating a size of residual data generated by dividing thetransmission data into the blocks each having the predetermined datasize; judging whether the calculated size of the residual data issmaller or not smaller than a minimum data size which a transmissiondestination apparatus can receive; and generating a block, whichincludes the residual data and whose data size is equal to or largerthan the minimum data size, by dividing the transmission data so as tomake the block, which includes the residual data, include a part of thetransmission data other than the residual data, in the case that it isjudged that the size of the residual data is smaller than the minimumdata size.